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Miller 330 A/BP won't strike arc without dragging tungsten on work

Hi all,
I have a 330 A/BP that we've been using for several years. It's always worked great. A couple of days ago, switched over to AC to weld some aluminum and two minutes into welding, it seemed that the power dropped off. The machine won't arc now on DC or AC unless I drag the tungsten on the work. I see nothing at the points like usual and there seems to be no current there. I'm thinking it's probably a diode issue. Anyone got any troubleshooting input?

Hi all,
I have a 330 A/BP that we've been using for several years. It's always worked great. A couple of days ago, switched over to AC to weld some aluminum and two minutes into welding, it seemed that the power dropped off. The machine won't arc now on DC or AC unless I drag the tungsten on the work. I see nothing at the points like usual and there seems to be no current there. I'm thinking it's probably a diode issue. Anyone got any troubleshooting input?

You may have some HV leakage.... they get pretty full of crud over the years... and a lot of that crud and grindings are metallic and conductive.. making great HV leakage paths..

if it were mine.... I would open the covers and look at it in a dark room with the lights turned off.... HF on.... you may very well have a high voltage leak....... look for blue corona sparks tracking off to ground where it should not be

could probably want dust/crud blown out with some compressed air while the covers are off ...

BTW.. have you downloaded the manual??

Last edited by H80N; 01-18-2014 at 03:45 PM.

.

*******************************************
The more you know, The better you know, How little you know......

“The bitterness of poor quality remains long after the sweetness of low price is forgotten”

Buy the best tools you can afford.. Learn to use them to the best of your ability.. and take care of them...

You may have some HV leakage.... they get pretty full of crud over the years... and a lot of that crud and grindings are metallic and conductive.. making great HV leakage paths..

if it were mine.... I would open the covers and look at it in a dark room with the lights turned off.... HF on.... you may very well have a high voltage leak....... look for blue corona sparks tracking off to ground where it should not be

could probably want dust/crud blown out with some compressed air while the covers are off ...

BTW.. have you downloaded the manual??

A few other thoughts. I am assuming when you "scratch" start the machine welds normally??? If this is true HF leaks as stated above could be a problem.
OR your HF capacitors may be junk. Sometimes one may "leak" and kill HF
with the symptoms you describe. If this were true you can disconnect the copper straps to them one at a time and HF will work with one in the circuit
at a reduced strength. Give it a try.....OR maybe your HF switch is no good.
Let me know I have recently done a LOT of work on these and am quite familiar with them.

More info

Originally Posted by NHTIG

A few other thoughts. I am assuming when you "scratch" start the machine welds normally??? If this is true HF leaks as stated above could be a problem.
OR your HF capacitors may be junk. Sometimes one may "leak" and kill HF
with the symptoms you describe. If this were true you can disconnect the copper straps to them one at a time and HF will work with one in the circuit
at a reduced strength. Give it a try.....OR maybe your HF switch is no good.
Let me know I have recently done a LOT of work on these and am quite familiar with them.

I opened up the machine already and looked for voltage leaks. I did not see any. I also don't see that oil is any oil leaking from the large capacitors. They look normal. The machine does not want to maintain full power arc on DC but seems to have full power on DC. Like I say, this problem started suddenly while welding aluminum on AC. We mostly do stainless steel so use DC mostly.

I opened up the machine already and looked for voltage leaks. I did not see any. I also don't see that oil is any oil leaking from the large capacitors. They look normal. The machine does not want to maintain full power arc on DC but seems to have full power on DC. Like I say, this problem started suddenly while welding aluminum on AC. We mostly do stainless steel so use DC mostly.

Did you blow it out and clean + regap the spark gaps...??

Last edited by H80N; 01-18-2014 at 06:03 PM.

.

*******************************************
The more you know, The better you know, How little you know......

“The bitterness of poor quality remains long after the sweetness of low price is forgotten”

Buy the best tools you can afford.. Learn to use them to the best of your ability.. and take care of them...

I opened up the machine already and looked for voltage leaks. I did not see any. I also don't see that oil is any oil leaking from the large capacitors. They look normal. The machine does not want to maintain full power arc on DC but seems to have full power on DC. Like I say, this problem started suddenly while welding aluminum on AC. We mostly do stainless steel so

use DC mostly.

I am a little confused,,"does not want to maintain full power arc on DC BUT seems to have full power on DC" How did you determine it has "full power" on DC?? I guess you mean it fires up then dies out?? You are using a foot pedal?? this problem as I understand it could be a bad connection or cable problem going to the foot pedal. The HF problem could still be a capacitor they do not have to leak to be bad. Matter of fact lots of them function OK when they are leaky. I guess for the DC issue you describe I would disconnect the foot pedal
and try running it in standard mode and see if the problem goes away??? Seems really strange to have an HF problem come about at the same time. The HF circuit is really not directly related to DC output. Hard to troubleshoot remotely. Try the capacitor test and see if you can get HF back.

More info

Originally Posted by NHTIG

I am a little confused,,"does not want to maintain full power arc on DC BUT seems to have full power on DC" How did you determine it has "full power" on DC?? I guess you mean it fires up then dies out?? You are using a foot pedal?? this problem as I understand it could be a bad connection or cable problem going to the foot pedal. The HF problem could still be a capacitor they do not have to leak to be bad. Matter of fact lots of them function OK when they are leaky. I guess for the DC issue you describe I would disconnect the foot pedal
and try running it in standard mode and see if the problem goes away??? Seems really strange to have an HF problem come about at the same time. The HF circuit is really not directly related to DC output. Hard to troubleshoot remotely. Try the capacitor test and see if you can get HF back.

I meant to say that the machine seems to lose power on AC when welding. DC power seems fine. I tried the machine with the remote switch off so the pedal was not in the circuit. Same thing happens. I will try a thorough cleaning tomorrow as well as the capacitor test. But I can tell I've got good welding current on DC with or without the pedal and current fades on AC with or without the pedal. I looked at the point gap and nothing is going on at the points. There is no current getting to them at all. I went so far as to short across the gap with a screwdriver while my partner was throwing an arc with the torch. There's no power there. I appreciate the input. I'll check caps. tomorrow and clean everything.

I meant to say that the machine seems to lose power on AC when welding. DC power seems fine. I tried the machine with the remote switch off so the pedal was not in the circuit. Same thing happens. I will try a thorough cleaning tomorrow as well as the capacitor test. But I can tell I've got good welding current on DC with or without the pedal and current fades on AC with or without the pedal. I looked at the point gap and nothing is going on at the points. There is no current getting to them at all. I went so far as to short across the gap with a screwdriver while my partner was throwing an arc with the torch. There's no power there. I appreciate the input. I'll check caps. tomorrow and clean everything.

When TIG welding and HF is not working the machine will sputter and act funky as it tries to maintain the arc. This is because as it switches between negative and positive cycles of the ac waveform and goes thru zero volts and without HF it tries to quit. SO..I think if you get HF going your problems may be solved.
HF problems are NOT limited to but most likely to be the capacitors, switch or HF transformer. Switch is unlikely if it does not function in either continuous or start mode. In start mode the control circuits come into play and that is a whole
different story I will not bore you with. Let me know I will try to monitor this tomorrow or if you like PM me with your phone number and I will give you a call.
Which will safe you lots of time.

More info

Originally Posted by NHTIG

When TIG welding and HF is not working the machine will sputter and act funky as it tries to maintain the arc. This is because as it switches between negative and positive cycles of the ac waveform and goes thru zero volts and without HF it tries to quit. SO..I think if you get HF going your problems may be solved.
HF problems are NOT limited to but most likely to be the capacitors, switch or HF transformer. Switch is unlikely if it does not function in either continuous or start mode. In start mode the control circuits come into play and that is a whole
different story I will not bore you with. Let me know I will try to monitor this tomorrow or if you like PM me with your phone number and I will give you a call.
Which will safe you lots of time.

I took out the points and cleaned them, then reinstalled them and reset the gap to 0.008. I blew out every area inside the machine (which was quite dusty). I rechecked to see just what I have going on. If I have the machine set on DC and drag start the TIG torch, it holds an arc fine. It will not jump any gap to start now, however, which it has always done before. I seem to have no AC. The machine will arc if you drag start but will not maintain the arc. It just sort of sputters and sounds similar to when you forget to turn on the gas before starting to weld but gas is flowing because I hear it at the cup. I see no arcing at the points at all, which I have always seen in the past. I have not checked any capacitors yet other than visually.

I took out the points and cleaned them, then reinstalled them and reset the gap to 0.008. I blew out every area inside the machine (which was quite dusty). I rechecked to see just what I have going on. If I have the machine set on DC and drag start the TIG torch, it holds an arc fine. It will not jump any gap to start now, however, which it has always done before. I seem to have no AC. The machine will arc if you drag start but will not maintain the arc. It just sort of sputters and sounds similar to when you forget to turn on the gas before starting to weld but gas is flowing because I hear it at the cup. I see no arcing at the points at all, which I have always seen in the past. I have not checked any capacitors yet other than visually.